java基础11（IO流）-字符流

时间：2023-03-10 04:32:05
java基础11（IO流）-字符流

转换流

由于字节流操作中文不是特别方便，所以java中提供了转换流

编码表：由现实世界的字符和对应的数值组成的一张表

编码：把看得懂的变成看不懂的(String-------byte[])

解码：把看不懂的变成看得懂的(byte[]-------String)

  • String-----bytes[]
import java.util.Arrays;

import java.io.UnsupportedEncodingException;

public class StringDemo{

	public static void main(String[] args)throws UnsupportedEncodingException{

		String s = "你好";

		//String-----bytes[]

/*

		byte[] bys = s.getBytes();//将字符串转换成字节数组

		System.out.println(Arrays.toString(bys));//输出结果：[-28, -67, -96, -27, -91, -67]

*/

/*

		byte[] bys = s.getBytes("GBK");//指定编码方式

		System.out.println(Arrays.toString(bys));//输出结果：[-60, -29, -70, -61]

*/

		byte[] bys = s.getBytes("utf-8");

		System.out.println(Arrays.toString(bys));//输出结果：[-28, -67, -96, -27, -91, -67]

	}

}
  • bytes[]-----String
import java.io.UnsupportedEncodingException;

public class StringDemo{

	public static void main(String[] args)throws UnsupportedEncodingException{

		String s = "你好";

	//	byte[] bys = s.getBytes();//默认是utf-8编码

		byte[] bys = s.getBytes("utf-8");

		//byte[] ---Sttring

//		String ss = new String(bys);//utf-8编码的，utf-8解码的

//		System.out.println(ss);//转换成字符串;输出结果是你好

		String ss = new String(bys,"GBK");//utf-8编的,GBK解码的

		System.out.println(ss);//输出结果是：浣犲ソ

	}

}

OutputStreamWriter



OutputStreamWriter(OutputStream out) :使用默认编码把字节流的数据转换为字符流

OutputStreamWriter(OutputStream out, String charseName)：根据指定编码把字节流数据转换成字符流

OutputStreamWriter(或FileWriter)写数据

public void write(int c):写一个字符

public void write(char[] cbuf):写一个字符数组

public void write(char[] cbuf,int off,int len):写一个字符数组的一部分

public void write(String str):写一个字符串

public void write(String str,int off,int len):写一个字符串的一部分

代码练习

import java.io.FileOutputStream;

import java.io.OutputStreamWriter;

import java.io.IOException;

public class OutputStreamWriteDemo{

	public static void main(String[] args)throws IOException{

		//创建对象

		OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream("/home/hadoop/a.txt"));

/*

		//写数据

		//public void write(int c):写一个字符

		osw.write("\na\n");

		osw.write(87);

*/

		//public void write(char[] cbuf):写一个字符数组

		char[] chs = {'a','b','c','d'};//不能使用双引号？

//		osw.write(chs);

		//public void write(char[] cbuf,int off,int len):写一个字符数组的一部分

//		osw.write(chs,1,3);

		//public void write(String str):

//		osw.write("自学java");

		//public void write(String str,int off, int len):写一个字符串的一部分

		osw.write("邬家栋自学java",3,6);

		osw.flush();

		osw.close();

	}

}

InputStreamReader

InputStreamReader(InputStream in) :用默认的编码读取数据

InputStreamReader(InputStream in, String charsetName) :用指定的编码读取数据

InputStreamReader(或FileReader)读取数据

int read():一次读取一个字符

int read(char[] chs):一次读取一个字符数组

代码练习

import java.io.FileInputStream;

import java.io.InputStreamReader;

import java.io.IOException;

public class InputStreamReadDemo{

	public static void main(String[] args)throws IOException{

		//创建对象

		InputStreamReader isr = new InputStreamReader(new FileInputStream("/home/hadoop/javatest/IO/OutputStreamWriteDemo.java"));

/*

		int ch = 0;

		while((ch = isr.read())!= -1){

			System.out.print((char)ch);

		}

*/

		//一次读取一个字符数组

		char[] chs = new char[1024];

		int len = 0;

		while((len = isr.read(chs)) != -1){

			System.out.print(new String(chs,0,len));

		}

		isr.close();

	}

}

字符流读写数据（复制文本文件）

import java.io.InputStreamReader;

import java.io.OutputStreamWriter;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.IOException;

public class CopyFileDemo{

	public static void main(String[] args)throws IOException{

		//封装数据源

		InputStreamReader isr = new InputStreamReader(new FileInputStream("/home/hadoop/a.txt"));

		//封装目的地

		OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream("/home/hadoop/b.txt"));

/*

		//方式一

		int ch = 0;

		while((ch = isr.read()) != -1){

			osw.write(ch);

		}

*/

		//方式二

		char[] chs = new char[1024];

		int len = 0;

		while((len = isr.read(chs)) != -1){

			osw.write(chs,0,len);

			osw.flush();

		}

		isr.close();

		osw.close();

	}

}

字符缓冲流BufferedWriter写数据

import java.io.BufferedWriter;

import java.io.FileWriter;

import java.io.IOException;

import java.io.FileOutputStream;

import java.io.OutputStreamWriter;

public class BufferedWriterDemo{

	public static void main(String[] args)throws IOException{

		//BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("bw.txt")));

		BufferedWriter bw = new BufferedWriter(new FileWriter("bw.txt"));

		bw.write("hello\n");

		bw.write("wujiadong\n");

		bw.close();

	}

}

字符缓冲流BufferedReader读数据

import java.io.BufferedReader;

import java.io.FileReader;

import java.io.IOException;

public class BufferedReaderDemo{

	public static void main(String[] args)throws IOException{

		//创建字符缓冲输入流对象

		BufferedReader br = new BufferedReader(new FileReader("bw.txt"));

/*

		//方式1

		int ch = 0;

		while((ch = br.read()) != -1){

			System.out.print((char) ch);

		}

*/

		//方式2

		char[] chs = new char[1024];

		int len = 0;

		while((len = br.read(chs)) != -1){

			System.out.print(new String(chs,0,len));

		}

		br.close();

	}

}

字符缓存流复制文件

import java.io.BufferedReader;

import java.io.BufferedWriter;

import java.io.FileReader;

import java.io.FileWriter;

import java.io.IOException;

public class CopyFileDemo{

	public static void main(String[] args)throws IOException{

		//

		BufferedReader br = new BufferedReader(new FileReader("a.txt"));

		BufferedWriter bw = new BufferedWriter(new FileWriter("b.txt"));

		//方式1

		//方式2

		char[] chs = new char[1024];

		int len = 0;

		while((len = br.read(chs)) != -1){

			bw.write(chs,0,len);

		}

		br.close();

		bw.close();

	}

}

特殊功能（一次读一行）

  • readLine(): 无换行符
  • newline(): 换行
import java.io.BufferedWriter;

import java.io.FileWriter;

import java.io.IOException;

import java.io.BufferedReader;

import java.io.FileReader;

public class BufferedDemo{

	public static void main(String[] args)throws IOException{

	//	write();

		read();

	}

	public static void read()throws IOException{

		BufferedReader br = new BufferedReader(new FileReader("bw2.txt"));

		String line = null;

		while((line = br.readLine()) != null){

			System.out.println(line);

		}

		br.close();

	}

	public static void write() throws IOException{

		BufferedWriter bw = new BufferedWriter (new FileWriter("bw2.txt"));

		for(int i=0;i<10;i++){

			bw.write("wujiadong");

			bw.newLine(); //换行

			bw.flush();

		}

		bw.close();

	}

}

复制文件

import java.io.BufferedReader;

import java.io.BufferedWriter;

import java.io.IOException;

import java.io.FileReader;

import java.io.FileWriter;

public class CopyFileDemo1{

	public static void main(String[] args)throws IOException{

		//封装数据源

		BufferedReader br = new BufferedReader(new FileReader("CopyFileDemo.java"));

		//封装目的地

		BufferedWriter bw = new BufferedWriter(new FileWriter("bw3.txt"));

		String line = null;

		while((line = br.readLine()) != null){

			bw.write(line);

			bw.newLine();

			bw.flush();

		}

		br.close();

		bw.close();

	}

}

练习1：复制文本文件

import java.io.FileReader;

import java.io.FileWriter;

import java.io.IOException;

import java.io.BufferedReader;

import java.io.BufferedWriter;

public class CopyFileDemo{

	public static void main(String[] args)throws IOException{

		String srcString = "bw3.txt";

		String desString = "wu.txt";

//		method1(srcString,desString);

// 		method2(srcString,desString);

//		method3(srcString,desString);

//		method4(srcString,desString);

		method5(srcString,desString);

	}

	//字符缓存流一次读写一个字符串

	private static void method5(String srcString,String desString)throws IOException{

		BufferedReader br = new BufferedReader(new FileReader(srcString));

		BufferedWriter bw = new BufferedWriter(new FileWriter(desString));

		String line = null;

		while((line = br.readLine()) != null){

			bw.write(line);

			bw.newLine();

			bw.flush();

		}

		br.close();

		bw.close();

	}

	//字符缓存流一次读写一个字符数组

	private static void method4(String srcString,String desString)throws IOException{

		BufferedReader br = new BufferedReader(new FileReader(srcString));

		BufferedWriter bw = new BufferedWriter(new FileWriter(desString));

		char[] ch = new char[1024];

		int len = 0;

		while((len = br.read(ch)) != -1){

			bw.write(ch);

		}

		br.close();

		bw.close();

	}

	//字符缓冲流一次读写一个字符

	private static void method3(String srcString,String desString)throws IOException{

		BufferedReader fr = new BufferedReader(new FileReader(srcString));

		BufferedWriter fw = new BufferedWriter(new FileWriter(desString));

		int ch = 0;

		while((ch = fr.read()) != -1){

			fw.write(ch);

		}		

		fr.close();

		fw.close();

	}

	//基本字符流一次读取一个字符数组

	private static void method2(String srcString,String desString)throws IOException{

		FileReader fr = new FileReader(srcString);

		FileWriter fw = new FileWriter(desString);

		char[] ch = new char[1024];

		int len = 0;

		while((len = fr.read(ch)) != -1){

			fw.write(ch, 0 ,len);

		}

		fr.close();

		fw.close();

	}

	//基本字符流一次读写一个字符

	private static void method1(String srcString,String desString)throws IOException{

		FileReader fr = new FileReader(srcString);

		FileWriter fw = new FileWriter(desString);

		int ch = 0;

		while((ch = fr.read()) != -1){

			fw.write(ch);

		}

		fr.close();

		fw.close();

	}

}

练习2：复制非文本文件的4种方法

import java.io.File;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.BufferedInputStream;

import java.io.BufferedOutputStream;

public class CopyImageDemo{

	public static void main(String[] args)throws IOException{

		//使用字符串作为路径

//		String srcFile = "1.jpg";

//		String desFile = "/home/hadoop/javatest/1.jpg";

		//使用File对象作为参数

		File srcFile = new File("/home/hadoop/1.jpg");

		File desFile = new File("/home/hadoop/javatest/1.jpg");

//		method1(srcFile,desFile);

//		method2(srcFile,desFile);

//		method3(srcFile,desFile);

		method4(srcFile,desFile);

	}

	//基本字节流一次读取一个字节

	public static void method1(File srcFile,File desFile)throws IOException{

		FileInputStream fis = new FileInputStream(srcFile);

		FileOutputStream fos = new FileOutputStream(desFile);

		int by = 0;

		while((by = fis.read()) != -1){

			fos.write(by);

		}

		fis.close();

		fos.close();

	}

	//基本字节流一次读写一个字节数组

	public static void method2(File srcFile,File desFile)throws IOException{

		FileInputStream fis = new FileInputStream(srcFile);

		FileOutputStream fos = new FileOutputStream(desFile);

		byte[] by = new byte[1024];

		int len = 0;

		while((len = fis.read(by)) != -1){

			fos.write(len);

			fos.flush();

		}

		fis.close();

		fos.close();

	}	

	public static void method3(File srcFile,File desFile)throws IOException{

		BufferedInputStream bis = new BufferedInputStream(new FileInputStream(srcFile));

		BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(desFile));

		int by = 0;

		while((by = bis.read()) != -1){

			bos.write(by);

		}

		bis.close();

		bos.close();

	}

	//字节缓冲流一次读取一个字节数组

	public static void method4(File srcFile,File desFile)throws IOException{

		BufferedInputStream bis = new BufferedInputStream(new FileInputStream(srcFile));

		BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(desFile));

		byte[] by = new byte[1024];

		int len = 0;

		while((len = bis.read()) != -1){

			bos.write(by);

			bos.flush();

		}

		bis.close();

		bos.close();

	}

}

练习3：将集合中的数据存储到文本文件

/*

 * 需求：将ArrayList集合中的字符串数据存储到文本文件

 *

 */

import java.util.ArrayList;

import java.io.BufferedWriter;

import java.io.IOException;

import java.io.FileWriter;

public class ArrayListToFileDemo{

	public static void main(String[] args)throws IOException{

		//创建集合对象

		ArrayList<String> array = new ArrayList<String>();

		array.add("java");

		array.add("python");

		array.add("scala");

		//封装目的地

		BufferedWriter bw = new BufferedWriter(new FileWriter("/home/hadoop/wu.txt"));	

		//遍历集合

		for(String s:array){

			bw.write(s);

			bw.newLine();

		}

		bw.close();

	}

}

练习4：把文本文件的数据存储到集合

/*

 * 需求：从文本文件中读取数据（一行为一个字符串数据）到集合中,并遍历集合

 *

 *

 */

import java.util.ArrayList;

import java.io.BufferedReader;

import java.io.FileReader;

import java.io.IOException;

public class FileToArrayListDemo{

	public static void main(String[] args)throws IOException{

		//封装数据源

		BufferedReader br = new BufferedReader(new FileReader("/home/hadoop/wu.txt"));

		//封装目的地

		ArrayList<String> array = new ArrayList<String>();

		//读取数据存储到集合中

		String line = null;

		while((line = br.readLine()) != null){

			array.add(line);

		}

		br.close();

		//遍历集合

		for(String s:array){

			System.out.println(s);

		}

	}

}

练习5：

/*

 * 需求：有一个文本文件存储了几个名称，写一个程序实现随机获取一个人的名字

 *

 */

import java.io.BufferedReader;

import java.io.FileReader;

import java.io.IOException;

import java.util.ArrayList;

import java.util.Random;

public class GetName{

	public static void main(String[] args)throws IOException{

		//把文本文件的数据存储到集合中

		BufferedReader br = new BufferedReader(new FileReader("/home/hadoop/wu.txt"));

		ArrayList<String> array = new ArrayList<String>();

		String line = null;

		while((line = br.readLine()) != null){

			array.add(line);

		}

		br.close();

		//产生一个随机索引

		Random r = new Random();

		int index = r.nextInt(array.size());

		//根据该索引获取一个值

		String name = array.get(index);

		System.out.println("幸运者是："+name);

	}

}

练习6：复制单级文件夹



import java.io.File;

import java.io.BufferedInputStream;

import java.io.BufferedOutputStream;

import java.io.IOException;

import java.io.FileInputStream;

import java.io.FileOutputStream;

public class CopyFolderDemo{

	public static void main(String[] args)throws IOException{

		//封装目录

		File srcFolder = new File("/home/hadoop/javatest/IO");

		File desFolder = new File("/home/hadoop/wu_test");

		//如果目的地文件夹不存在就创建

		if(!desFolder.exists()){

			desFolder.mkdir();

		}

		//获取该目录下的所有文本的File数组

		File[] fileArray = srcFolder.listFiles();

		//遍历该File数组，得到么一个File对象

		for(File file:fileArray){

			//System.out.println(file);

			//数据源：/home/hadoop/javatest

			//目的地：/home/hadoop/wu_test

			String name = file.getName();

			File newFile = new File(desFolder,name);

			copyFile(file,newFile);

		}

	}

	private static void copyFile(File file,File newFile)throws IOException{

		BufferedInputStream bis = new BufferedInputStream(new FileInputStream(file));

		BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(newFile));

		byte[] by = new byte[1024];

		int len = 0;

		while((len = bis.read(by)) != -1){

			bos.write(by,0,len);

		}

		bos.close();

		bis.close();

	}

}

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